Re: [PATCH 43/43] xfs: export max_open_zones in sysfs

Darrick J. Wong
2025-02-07T00:53:01Z

On Thu, Feb 06, 2025 at 07:44:59AM +0100, Christoph Hellwig wrote:
> Add a zoned group with an attribute for the maximum number of open zones.
> This allows querying the open zones for data placement tests, or also
> for placement aware applications that are in control of the entire
> file system.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

It occurs to me -- what happens to all this zoned code if you build
without RT support?

Creating a whole sysfs kobj just to export a single attribute seems a
little overkill but I guess that beats revving the fs geometry ioctl.

Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
> fs/xfs/xfs_mount.h | 1 +
> fs/xfs/xfs_sysfs.c | 40 ++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 41 insertions(+)
>
> diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
> index 7c7fd94375c1..390d9d5882f4 100644
> --- a/fs/xfs/xfs_mount.h
> +++ b/fs/xfs/xfs_mount.h
> @@ -277,6 +277,7 @@ typedef struct xfs_mount {
> #ifdef CONFIG_XFS_ONLINE_SCRUB_STATS
> struct xchk_stats *m_scrub_stats;
> #endif
> + struct xfs_kobj m_zoned_kobj;
> xfs_agnumber_t m_agfrotor; /* last ag where space found */
> atomic_t m_agirotor; /* last ag dir inode alloced */
> atomic_t m_rtgrotor; /* last rtgroup rtpicked */
> diff --git a/fs/xfs/xfs_sysfs.c b/fs/xfs/xfs_sysfs.c
> index c3bd7dff229d..797a92908647 100644
> --- a/fs/xfs/xfs_sysfs.c
> +++ b/fs/xfs/xfs_sysfs.c
> @@ -13,6 +13,7 @@
> #include "xfs_log.h"
> #include "xfs_log_priv.h"
> #include "xfs_mount.h"
> +#include "xfs_zones.h"
>
> struct xfs_sysfs_attr {
> struct attribute attr;
> @@ -701,6 +702,34 @@ xfs_error_sysfs_init_class(
> return error;
> }
>
> +static inline struct xfs_mount *zoned_to_mp(struct kobject *kobj)
> +{
> + return container_of(to_kobj(kobj), struct xfs_mount, m_zoned_kobj);
> +}
> +
> +static ssize_t
> +max_open_zones_show(
> + struct kobject *kobj,
> + char *buf)
> +{
> + /* only report the open zones available for user data */
> + return sysfs_emit(buf, "%u\n",
> + zoned_to_mp(kobj)->m_max_open_zones - XFS_OPEN_GC_ZONES);
> +}
> +XFS_SYSFS_ATTR_RO(max_open_zones);
> +
> +static struct attribute *xfs_zoned_attrs[] = {
> + ATTR_LIST(max_open_zones),
> + NULL,
> +};
> +ATTRIBUTE_GROUPS(xfs_zoned);
> +
> +static const struct kobj_type xfs_zoned_ktype = {
> + .release = xfs_sysfs_release,
> + .sysfs_ops = &xfs_sysfs_ops,
> + .default_groups = xfs_zoned_groups,
> +};
> +
> int
> xfs_mount_sysfs_init(
> struct xfs_mount *mp)
> @@ -741,6 +770,14 @@ xfs_mount_sysfs_init(
> if (error)
> goto out_remove_error_dir;
>
> + if (xfs_has_zoned(mp)) {
> + /* .../xfs/<dev>/zoned/ */
> + error = xfs_sysfs_init(&mp->m_zoned_kobj, &xfs_zoned_ktype,
> + &mp->m_kobj, "zoned");
> + if (error)
> + goto out_remove_error_dir;
> + }
> +
> return 0;
>
> out_remove_error_dir:
> @@ -759,6 +796,9 @@ xfs_mount_sysfs_del(
> struct xfs_error_cfg *cfg;
> int i, j;
>
> + if (xfs_has_zoned(mp))
> + xfs_sysfs_del(&mp->m_zoned_kobj);
> +
> for (i = 0; i < XFS_ERR_CLASS_MAX; i++) {
> for (j = 0; j < XFS_ERR_ERRNO_MAX; j++) {
> cfg = &mp->m_error_cfg[i][j];
> --
> 2.45.2
>
>